The present invention relates to intraocular lenses (IOLs) and a method for making and using the same. More particularly, the present invention relates to accommodating IOLs designed for refractive correction in aphakic eyes where a diseased natural lens is surgically removed, such as in the case of cataracts.
IOL implants have been used for many years in aphakic eyes as replacements for diseased natural crystalline lenses that have been surgically removed from the eyes. Many different IOL designs have been developed over past years and proven successful for use in aphakic eyes. Successful IOL designs to date primarily include an optic portion with supports therefor, called haptics, connected to and surrounding at least part of the optic portion. The haptic portions of an IOL are designed to support the optic portion of the IOL in the lens capsule, anterior chamber or posterior chamber of an eye.
Commercially successful IOLs have been made from a variety of biocompatible materials, ranging from more rigid materials such as polymethylmethacrylate (PMMA) to softer, more flexible materials capable of being folded or compressed such as silicones, certain acrylics, and hydrogels. Haptic portions of the IOLs have been formed separately from the optic portion and later connected thereto through processes such as heat, physical staking and/or chemical bonding. Haptics have also been formed as an integral part of the optic portion in what is commonly referred to as xe2x80x9csingle-piecexe2x80x9d IOLs.
Softer, more flexible IOLs have gained in popularity in more recent years due to their ability to be compressed, folded, rolled or otherwise deformed. Such softer IOLs may be deformed prior to insertion thereof through an incision in the cornea of an eye. Following insertion of the IOL in an eye, the IOL returns to its original pre-deformed shape due to the memory characteristics of the soft material. Softer, more flexible IOLs as just described may be implanted into an eye through an incision that is much smaller, i.e., 2.8 to 3.2 mm, than that necessary for more rigid IOLs, i.e., 4.8 to 6.0 mm. A larger incision is necessary for more rigid IOLs because the lens must be inserted through an incision in the cornea slightly larger than the diameter of the inflexible IOL optic portion. Accordingly, more rigid IOLs have become less popular in the market since larger incisions have been found to be associated with an increased incidence of postoperative complications, such as induced astigmatism.
After IOL implantation, both softer and more rigid IOLs are subject to compressive forces exerted on the outer edges thereof from natural brain-induced contraction and relaxation of the ciliary muscle and increases and decreases in vitreous pressure. Compressive forces of this kind are useful in a phakic eye for focusing the eye at various distances. Most commercially successful IOL designs for use in aphakic eyes have single focus optic portions that are fixed and focus the eye at only a certain fixed distance. Such single focus IOLs require the wearing of glasses to change the focus of the eye. A few bifocal IOLs have been introduced to the commercial market but suffer from the disadvantage that each bifocal image represents only about forty percent of the available light and the remaining twenty percent of the light is lost to scatter, which provides lessened visual acuity.
Because of the noted shortcomings of current IOL designs, there is a need for accommodating IOLs designed to provide multifocal visual imaging in aphakic eyes without the aid of eyeglasses.
An accommodating intraocular lens (IOL) made in accordance with the present invention has an optic portion with an outer peripheral edge and two, three or four haptic elements for supporting the optic portion in a patient""s eye. A lens having two haptic elements is balanced by having a haptic element formed or attached on two opposed edges of the optic portion. A lens having three haptic elements is balanced by having a set of two haptic elements formed or attached on one edge of the optic and the third haptic element formed or attached on an opposite edge of the optic. A lens having four haptic elements is balanced by having a set of two haptic elements formed or attached on one edge of the optic and a set of two haptic elements formed or attached on an opposite edge of the optic. Each haptic element has an attachment portion that permanently connects the haptic element to the outer peripheral edge of the optic portion. If the haptic element is of a looped design, the haptic element has generally two attachment portions that permanently connect the looped haptic element to the outer peripheral edge of the optic portion. In the case of lenses having three or four looped haptic elements, a set of two looped haptic elements may have three attachment portions rather than four. In such a case, one of the three attachment portions is common to each of the two looped haptic elements in the set. Each haptic element whether of a loop design or not includes a flexible central portion located between the attachment portion and a contact plate. The contact plate is designed to engage an inner surface of a patient""s eye. The flexible central portions that extend between the contact plates and the attachment portions allow the optic portion of the lens to move or to adjust to pressures exerted on the lens within the eye. Additionally, within these flexible central portions, each haptic element is designed to have less resistance to bending in a plane generally parallel to the optical axis of an eye than in a plane generally perpendicular to the optical axis of an eye. By providing haptic elements with this type of flexibility characteristic, the present IOL maximizes axial displacement of the optic portion along the optical axis of the eye when compressive forces are exerted against the IOL. By increasing the subject IOLs movement along the optical axis of an eye, multifocal visual imaging without the aid of eyeglasses is achieved.
Accordingly, it is an object of the present invention to provide accommodating intraocular lenses for use in aphakic eyes.
Another object of the present invention is to provide accommodating intraocular lenses for use in aphakic eyes, which maximize axial displacement of the optic portions of the lenses along the optical axis of the eyes.
Another object of the present invention is to provide accommodating intraocular lenses for use in aphakic eyes, which minimize damage to tissues in the interior of the eyes.
Still another object of the present invention is to provide accommodating intraocular lenses, which are resistant to decentration within the eyes.
These and other objectives and advantages of the present invention, some of which are specifically described and others that are not, will become apparent from the detailed description, drawings and claims that follow, wherein like features are designated by like numerals.